Lissencephaly
| ICD9 = | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | MeshID = }} Lissencephaly, which literally means smooth brain, is a rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a lack of development of brain folds (gyri) and grooves (sulci).Dobyns, WB. Developmental aspects of lissencephaly and the lissencephaly syndromes. Birth Defects Orig Artic Ser 1987; 23:225. It is a form of cephalic disorder. Terms such as 'agyria' (no gyri) or 'pachygyria' (broad gyri) are used to describe the appearance of the surface of the brain. Children with lissencephaly are severely neurologically impairedBauman, ML. Neuroembryology--clinical aspects. Semin Perinatol 1987; 11:74. and often die within several months of birth.Jones, KL. Smith's Recognizable Patterns of Human Malformation, 6th ed. Elsevier Saunders, Philadelphia 2006. Symptoms Affected children display severe psychomotor retardation, failure to thrive, seizures, and muscle spasticity or hypotonia.Jones, KL. Smith's Recognizable Patterns of Human Malformation, 6th ed. Elsevier Saunders, Philadelphia 2006. Other symptoms of the disorder may include unusual facial appearance, difficulty swallowing, and anomalies of the hands, fingers, or toes. Diagnosis The diagnosis of lissencephaly is usually made at birth or soon after by ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI). Before birth, complex ultrasounds performed routinely during pregnancy may indicate the presence of cerebral abnormality, but this method of diagnosis is not reliable, and an absence of abnormal cerebral pathology should only inspire cautious optimism at best. In any case, diagnosis by ultrasound probably cannot be reliably made until 26 to 28 weeks, when the normal gyri and sulci become well defined. Up to this time, the fetal brain normally has a smooth appearance.Dorovini-Zis K; Dolman CL. Gestational development of brain. Archives of Pathologic Laboratory Medicine 1977 Apr;101(4):192-5. If lissencephaly is suspected, chorionic villus sampling can test for some lissencephaly variants, but only those with a known genetic mutation. Causes Causes of lissencephaly can include viral infections of the uterus or the fetus during the first trimester, or insufficient blood supply to the fetal brain early in pregnancy. There are also a number of genetic causes of lissencephaly, including mutation of the reelin gene (on chromosome 7),Hong SE, Shugart YY, Huang DT, Shahwan SA, Grant PE, Hourihane JO, Martin ND, Walsh CA. (2000) Autosomal recessive lissencephaly with cerebellar hypoplasia is associated with human RELN mutations. Nat Genet. 26(1):93-6. PMID 10973257 as well as other genes on the X chromosome and on chromosome 17. Genetic counseling is usually offered if there is a risk of lissencephaly, coupled with genetic testing. Classification The spectrum of lissencephaly is only now becoming more defined as neuroimaging and genetics has provided more insights into migration disorders. There are around 20 different types of lissencephaly which make up the spectrum. Other causes which have not yet been identified are likely as well. Different systems for classifying lissencephaly exist. One major distinction is "classic" (type I) vs. "cobblestone" (type II), but some systems add additional forms that fit into neither of these categories. Some types of lissencephaly are described below (OMIM numbers are included where available): Treatment Treatment for those with lissencephaly is symptomatic and depends on the severity and locations of the brain malformations. Supportive care may be needed to help with comfort and nursing needs. Seizures may be controlled with medication and hydrocephalus may require shunting. If feeding becomes difficult, a gastrostomy tube may be considered. Prognosis The prognosis for children with lissencephaly varies depending on the degree of brain malformation. Many individuals show no significant development beyond a 3- to 5-month-old level. Some may have near-normal development and intelligence. but with modern medications and care, some children live into their teens. Respiratory problems are the most common causes of death. External links * * Lissencephaly.org.uk * Lissencephaly Launch Pad (support) * Lissencephaly, generic term (pdf document) - concise and thorough classification of lissencephaly by prof. Alan Verloes. References Category:Congenital disorders Category:Developmental disorders Category:Nervous system development